Control system



Dec. 2, 1941. I TAYLOR 2,264,865

common sys'rniu I Filed May 24, 1939 Fig.1. J5

Inventor: Laurens Afag loq bgy fili l His A tofnesy Patented Dec. 2, 1941 i wws CONTROL SYSTEM Lani-cm A. Taylor, Schenectady, N. Y alaignor to General Electric Company, a

New York corporation Application m 24, 1939, serial No. zrssoi (Cl. ca -s1) 13 Claims.

My invention relates to a control system for power plants and 'more particularly to a speed and synchronizing control system (or controllin a plurality of engine-propeller combinations used to furnish propulsive power for a vehicle, such as an airplane.

An-obj ect of my invention is the provision of control means for a plurality of power plants arranged so thateachvpower plant may be manually and independently controlled, or one or,

more 01! the power plants automatically controlled to obtain synchronous operation of the power 1 plants.

Another object of my invention is the provision, in combination with an adjustable speed controlling means, such as a governor for each power plant, oi electrical devices for adjusting the'various governors, such electrical devices being capable ot operation as electrical diiierential devices for automatic synchronizing control and as reversible motors for independent manual control of each of the respective power plants. A iurther object 01 my invention is .the propower plants utilized to furnish propulsive pbwer for a single vehicle or airplane. Although I have illustrated a dual power plant or two engine arrangement, it is to be understood that the control system embodying my invention may be extended to eiiect the control of three, four or more power plants as desired.

Asshown, the pitch settings of the variablepitch propellers II and It are controlled respectively by the engine-driven governors II and ll 7 in a manner well known in the'art. For the purposes of this description, it will 'sufllce to say that the governors I4 and It may be 01' the centriiugal tiyball type having a speeder spring for v loadingthe fiyballs, the loading of this speeder spring being adjustable to change the flyball position for any given engine speed. The flyballs of each governor control the pitch changing mechanism of the corresponding controllable vision of interlocking means to enable the manual control of a selected one of the power plants by operating its. electrical device as an independent reversible motor and for simultaneously rendering impossible such independent manual control of the other electrical devices, when the other electrical devices are operating as differential devices during automatic synchronizing control 01'.

their respective power plants, A still iurther object of my invention is the provision of control limiting means to render each of the electricaLdevices inoperative if prede- E termlned control limits in the control exercised over their respective power plants are exceeded. either when the electrical devices are operating as diiierential devices or "as independent manually controlled reversible motors. Further objects of my invention will becom apparent from the following specificationand tor a more complete understanding oi my invention reierence should be hadto the accompanying drawing in which Fig. l is a schematic wiring M diagram of a control system embodying my invention arranged -ior the control of a, pair of power plants; and Fig. 2 is'an elevational view of an interlocking device for the switching means.

Referring to the drawing, 1 have shown my invention in one form as applied to the control of a plurality of power plants; such as a pair of airplane engines II and il, driving respectively the controllable pitch propellers l2 and II. The

engines I0 and It may constitute two separate pitch propeller in such a manner as to change the pitch of the propeller to vary the load upon the engine in response to variation in the speed of the engine from a predetermined value, depending upon the adjustment of the speeder spring. Suitable means including the translatable rods Ilt and I1 are "operatively connectedwith the speeder springs of the respective governors l4 and I! for adjustingthe setting of the corresponding flyballs. It should now be ap parent that translation oi. either of the rods It or II will adjust the corresponding governorll or II by changing the load on its speeder spring and thereby set a diiierent speed for the enginepropellercombination by accordingly altering the pitch of the respective propeller through its pitchchanging mechanismi Suitable movement or the rods Ii and I! to adjmt the governors l4 and ii is effected through the threaded members It and I! which are movable back and forth relative to their fixed mounting members 20 and I I .upon rotationgoi the gears 22 and I3 secured on the respective right-hand ends of the threaded members It and It. The

gear 22 is rotated in one direction or the other by an electrical motor device It whose operation will be more fully described hereinafter. The motor device It. is connected through the shaft 2'! carrying a pinion 28 to a gear 29 through suitable gear'ing It. The gear 2! is secured to the right-hand end of a shaft ll which has secured at its leit end a clutch plate 32. A slidable clutch member 33, shown in the disengaged position, may be engaged with the clutch plate 32, for operating or driving a shaft 34 which has secured at its left end a pinion 35 meshed with the gear :2. The shaft :4 a journaled in a iixed member of,the-engine II.

from the generator 35.

ll provided with a serrated axial face which ens les a similar. serrated face on the movable clutch member I! to act as a brake tending to hold the shaft 34 against rotation when the clutch It is disconnected. The movable clutch member ll may be connected to the shaft 34 .by a key and spline and is movable longitudinally from the dise cased position shown into clutching engages ment with-the clutch ,plate 82 by an operating member I'I pivoted on a pin II, the operating member I! being spring-biased to the position 1 shown and rotatable ina clockwise direction upon energization of the solenoid windings It. In

1 other words, I have provided a magnetically operable brake and clutch combination which serves 'to ounce and disconnect the electric motor device 2| the gear 22 for translating the rod it back or forth governor ll.

Similarly, an electric motor device it serves to drive the gear {3, the threaded member I! and the governor speeder-spring adjusting rod II to adjust the speeder spring of the through a shaft 42, the gearing It, a shaft 44,

[the clutch and brake members 45, a shaft ll and a pinion l1 meshed with the gear 23. Also, the solenoid windings It are provided for magnetically operating an actuating arm 4! operatively to engage the clutch when the solenoid windings 48 are energized, In this manner, and as will be more fully described hereinafter, the rotational forces ofthe electrlcmotor devices It and ll are directly transmittedfor adjusting the respective governors II and II and thereby the speedofthe engines-ll andll.

The electric motor devices It and are each provided with separately energizable stator and rotor windings which, as shown. comprise the poly-circuit stator II and the poly-circuit rotor ll of the electrical motor device it and the polycircuit stator Iii and the poly-circuit rotor ll 0! the electrical motor device ll. During automatic operation of the control system when it is desired to synchronizethe speed of one engine 'withrespecttotheothenorinasystemhaving more than two engines, to synchronize a plurality of engines with respect to the speed of one engine, each of the electric motor devices ofthe respective engines to be synchronized to a. reference speed established by the reference or master engine is operated as a diflerential motor supplied by a pair of generators and is subjected to the eiiects of frequency difference or phase differshown in the two engine system of Fig. 1, if it is desired to synchronize the engine II with rell will be operated as a differential motor. One setof windings of the differential motor ll is energized by an impulse generator ll, shown as r a three-phase generator, driven'at a speed bearinga direct'relation to the speed of the engine It and its other set of windings is energized by a similar generator I! driven by the engine it at a speed bearing a direct relation to the speed As shown, I prefer to energize the stator winding I! of the electric motor device a,as4,aos a e fThe operation of the electric motor devices It and II as diiferential motors will become apparent from the description hereinafter, but at this point it may be well to understand that a "selector" switch 51 is provided to. enable the operator to designate one or the other of the engines II and II as a master speed, controlling engine. Also, a manual-automatic" switch It is provided to enable the operator to make the final,

circuit connections after a particular engine has been designated as the master through the -selector" switch 51. a j

m additionto the automatic synchronizing of the engines II and l I, means are provided for effecting direct manual control of the speed of the engines It and I I, respectively, independently I trol system has been disconnected by turning the "manual-automatic switch II to its "manual" position and when the synchronizing system is in operation but the selector switch I! has been 1 operated to the position 10 shown, thereby desighating the engine i l as the master engine. Similarly. the "manual control'switoh It may be used to control the electric motor device II as an independent manually controllablemotor both when the synchronizing system has been disconnected by turning the manual-autumn switch II to its "manuaPpositionand when the synchronizing system is connected but the "selector" switch I! has been turned to the position 11 shown by dotted lines, thereby designating engine ll asthemasterengine.

i ences between these generators.- For instance as spect to the engine it, the electric motor device v 'II from its generator I while supplying the/ rotor winding ll of the electric motor device ll from the generator ll; Similarly, if the engine s is to be synchronizedwith reference to the engine II, I preferrto supply the electric motor device 28 by energizing the stator winding 50 from the generator I and the rotor winding llv With the above understanding of the elements included in this embodiment of my invention, the operation of the system itself and the mannerinwhich automatic synchronizing control, independent manual control, selection or designation of a master and manual control of the engines is eil'ected will be readily understood iromthe description which follows:

Assume now that the engines It and II are operating at speeds determined by their respective governors l4 and II and that their respective generators II- and II are being correspond- .ingly' driven. Preferably, the generators II and II are multiphase alternating current generators having one phasegrounded'. In'order-to s'ynchronwe one engine with respect to the other, a suitable adjustment 01' its governor must be made. For instance, if it is desired to synchronize the engine H with respect to the engine II, the governor I! must be adjusted to change the speed of the engine ll accordingly. To designate the engine III as the master engine which establishes the reference-or synchro ous speed,

the posi-" tion 10 shown. At this point, the circuits are merely preliminarily connected ready to operate the electric motor device 4| as a diii'erential the "seleotor switch" is-operated motor subjected to the effects of phase diiferenoe between the outputs of the generators N and II Y when the "manual-automatic" switch I is moved to its automatic".position. The engine speeds 7! determine the phase relation of the generators 7 no difierential motor ll will occur. Otherwise u and u. n the gem are the same, erators will'be in phase and opera phase difierence willcause the difierential motor ll until the appropriately adjusted to synchronise ginesltandllandtheirgenera rs ll. Upon selectionoi the engine II as a master engine 'by the selector switch II, the manualautomatic" switch I! may be moved clockwise to its "automatic position. Immediately the stator I! of the electric motor device it is supplied with three-phase power from the generator I oi'theengine ll. Agronmdconnection It serves to connect the right-handbrush oi the generator It to the right-hand vterminal oi the stator 52 by conductor 08 connected to the ground 2. The middle brush the generator "is conneixted to themiddie terminal of the stator 2 in a circuit which includes irom the generator a conductor '4, the normally-closed op'crationoi I interlock contacts", the conductors Cl and 01 connected to the movable contact ll of the "manuni-automatic" switch It. a fixed switch contact 80, a conductor II, a fixed "selector" switch contact II, a movable switch contact 12, a connection II and a movable switch contact II, a fixed switch contact ll, theconductors It and II and through a conductor II to the middle terminal oi the stator I2. As readily seen. the circuit Just described'irom-the generator I! also serves to energize through theconductor II the middle winding oi the clutch-operating solenoid ll, the right-hand winding oi the clutch-operating sole noid 4| being energizedvirom the ground connection l2. The left-hand terminal of the genings of the clutch solenoid are energised from the generator II to engage the clutch 4|, and the electric motor device ll is subjected to the eiiects oi phase difi'erences between the outputs ot the generators l4 and II to operate as'a difierential motor to! appropriately adjusting the ..governor ll to'maintainthee'nginell inmerator It is connected to the leit-l'iand terminaloi the stator l2 by a circuit which from the generator includes the conductors It and t0, the normally closed interlock contacts ll, theconductors l2 and 83, the movable and fixed switch contacts 84 and ll, a conductor ll, the fixed and movable switch contacts l1 and 88, a connection 88, the movable and fixed switch contacts 90 and ii, the conductors l2 and II and bya conductor 94 to the left-hand terminal or the stator 52. In additiomthe above described circuit serves to energize the left-hand winding of the clutch solenoid it through the-conductor I. Thus it is seen that simultaneously with the energization oi the stator II by the generator ,the three-phase windings of the clutch solenoid I! are also energized and the clutch", moved from its disengaged position shown to an engaged position for connecting the shafts and ll.

The three-phase connection from the generaton" to the rotor ll of the electric motor device generator 54 is connected to the left-hand terminal oi the rotor II by a circuit which from thegenerato'r includes a conductor III, the normally-closed interlock contacts III, the conductors I03 and vI, the fixed and movable switch contacts I" and till, a connection I", the movable and fixed switch contacts I and lll,a conductor III. the movable and fixed switch contacts Ill and III and by a conductor Ill-to the left-hand terminal oi the rotor 53. The left-- hand brush oi the generator I is connected to chronism with the engine ll.'-Depending upon the speed and phase relationship of the generators I4 and II, the difi'erential motor 4| will operate in one direction or the other to move the threaded member II and the adjusting rod ll back or iorth as required. As soon as the speeds or the engines It and II are'in synchronism'. the generators II and II will be-in phase and the diil'erential motor ll will cease to operate; the synchronizing operation then being completed. Obviously any change in speed oi the.

engine It relative to the engine H, such as will occur it the speed ot-the engine It is manually adiusted in a manner described more fully hereinaiter. will immediately eii'ect operation of the diilerential motor ll until the engine It is restored to synchronism with the engine ll.

Ii instead of designating the engine II as master engine. it is desired to select the engine It as the master engineior establishing the reierence speed, this may be done by turning the "selector" switch 51 in a clockwise direction to point 11. device 4| drops out of circuit and the electric motor device 28 is connected in circuit and supplied on its stator SI from its generator 54 and on its rotor SI from the generator II. The .cir-

cuits from the generator 54 to the stator ill oi the electric motor device 26 may be traced as follows: The right-hand brush or the generator I4 is connected through the ground connections I! by a conductor I it to the right-hand terminal oi the stator 80. The middle brush oi the generator II is connected to the middle terminal 01' the stator I. by a circuit which from the generator includes the conductor Ill, the normally-closed interlock contacts I", the conductors Ill and Ill. the movable and fixed switch contacts I32 and D3,]! conductor I", the fixed and movable contacts I" and 12, the connection ll, the movable and fixed contacts 14 and I" and by the conductors I31 and ill through the conductor I" to the middle terminal of the stator II. The left-hand brush 0! the generator II is connected to' the left-hand terminal of stator I by a circuit which includes from the gen-" erator the conductor I'll, the normally closed interlock contacts Hi,- the. conductors ill and N0, the movable and fixed switch contact Ill and La conductor I, the fixed and movable to the left-hand terminal oi the stator II. Also,

it should now be apparent that the three coils oi the clutch operating solenoid 39 have been energized from thegenerator 54 through the 3 themiddie'terminaloitherotor libyacircuit- Immediately then the electric motor H terminal of the stator 80 by a circuit which from the generator includes the conductor II4, the normally-closed interlock contacts III, the conductor IIO, the up" contacts I14 and by the conductors I41 and l48 to the left-hand terminal of the stator 50. The middle brush the generator 54 is now connected to the middle terminal or the/stator so by a circuit which from the generator includes the conductor IN, the normally closed interlock contacts I02, the conductor I08, the up" contacts I'll, the conductor I80, and through the conductor I89 to the middle terminal of the stator 50. The right-hand terminal of the stator 50 is 'again energized through the conductor I80 and the ground connections 82 from the right-hand brush of the generator 84. Thus it appearsthat the manual" switch 58 in the down" position will cause operation of the electric motor device 28 in one direction as an independent manually controlled induction motor while in the up" position, by reversing two leads irom the generator 54, will cause operation of the electric motorv device in the other direction also as an independent manually controlled induction motor. Simultaneously with the energization of the stator from the generator 54, the three windings of the clutch operating solenoid are energized from the live leads I98 and I41 and by the ground connection 52 to cause the clutch 38 to engage. In this manner the motor forces of the electric motor. device 28 are applied through the engaged clutch 38 to move the translatable adjusting rods I6 for setting the governor I4.

Similarly,with the engine II operating as the master engine as described in the foregoing or with the synchronizing system disconnected, the

manual switch 80 may be actuated from its controlling the setting oi its respective governor or II. Thuswiththeswitchll inthismanual position and the devices 20 and 4| thus disconnectedtrom the system, the device 28 may be operated as a motor in either direction as previously described by moving the switch 58 (mm its mid-position shown inthe drawing to its upper position or to its lower position depending upon the direction of rotation desired. This short circuits one winding of the device 26 and connects the device 28 tor operation as a motor to the generator 54, the engine I0 of course being, assumed to be running.

In a similar manner, operation of the switch 00 from the mid-position shown to its upper or lower position as previously described connects the device H to the generator 54 for operation as a motor in either direction depending upon the direction of movement of the switch 80 whereby the governor I5 may be adjusted as desired by manual control.

Also, as previously described in detail, when the engine I0 is operated as a master speed control engine, the switch 51 being thrown to the position required for operation of the engine I0 as a master, the device 28 is not electrically con nected with the synchronizing system and can be operated at that time as a motor by means of the switch 58 to adjust the speed oi the master engine I0- Likewise, as previously described, when the engine II is operating as a master speed control engine, the switch 51 being thrown to establish the required synchronizing connections, the motor device I is not connected with the synchronizing system and can be operated as a reversing motor by means of the manual switch 60 to adjust the speed of the master engine II. In each case, when the speed of the master engine is adjusted, the speed of the other engine is automatically given a corresponding adjustment through the synchronizing system.

As illustrated in Fig. 2, special interlocking means are provided to ensure the correct operation oi. the switches 58 and dependent upon middle terminal of the rotor 58 through the conductor I21, the respective down or up contacts I80 and I83, a conductor I86 and through the ground connections 62 and the conductor 1" to the right-hand terminal of the rotor 58. Also, the stator 52 is supplied through the respective down" contacts I8I and I82 or the respective.

up contacts I84 or I05 and the ground connections 82 with three phase power from suitable electric supply connections as shown from the generator 54 in circuits including the interlock contacts 85 and 8I similar to those described in connection with the electric .motor device 28. In this manner the electric motor device 4I is convertible to an independent manu-' power from the generator 55 upon operation of the manual switch 80.

It the manual-automatic switch 50 is moved to its manual position to disable the synchronizing system bydisconnecting the electric motor device 20 or H from the generator 54 or 55, as the case may be, then either or both of the electric motor devices 28 and H is operable as a manually controlled reversing, motor for independently the relative positions of the switches 51 and 58. As shown, the interlocking means comprises the crank arms I and HI which are respectively secured to the switches 51 and 58 for rotation therewith when either of these switches is operated. The crank arm I90 is connected to an elongated cam arm I88 by a pin I94 loosely fitted in a notch at the right-hand end of the cam arm I98. Similarly, the crank arm I8I is connected to a cam arm I55 by a pin I98 loosely fitted in a notch in the left-hand end of the cam arm 9 I95. The cam arms I88 and I95 extend toward each other and are held in side-by-side sliding relationship by the pins I9I which fit into elongated slots I88 in these arms. 'Each of the cam .arms I88 and I85 is provided with a pair of 200 engaging a recessed portion of the manual" 0 switch I to hold this switch in its neutral position. The locking arm 208 which has been I moved.counterclockwise by the cam surface'lll 'ot the cam arm I08 is'shown in its unlocked position with its pin 201 out 0! engagement with the greases mlly deenergizing the electric motor device Suitable limit switches m and m are provided for operation by the translatable gear :2

moved to the position 10 wherein the engine ll is designated as a..master en ine.

I. operating as a master, it is desirable that the operation of the electric motor device ll as a differential motor in the synchronizing operation not be inadvertently interfered with. To this end it is necessary to lock the "manual" switch It in its neutral position and prevent this switch from being accidentally actuated to one of its operated positions. As shown, the looking arm "lend its pin 208 perform this service. Meanwhile the manual switch ll-is-free for actuation should the operator desire to convert the electric motor device It to an independent manually controlled motor for controlling the setting of the governor Ilon the master engine II. If the selector" switch 51 is moved clockwise to its selector? position 11, the cam face I will be moved to the right out of contactwith the roller 2" of th locking arm I" and immediately the spring 20! will rotate this locking arm in a counterclockwise direction to its locking position to prevent actuation of the manual'fi, switch It. Simultaneously the cam face 200 will be moved to the right into engagement with the roller 20! of the locking arm 2. The resulting clockwise rotation of the locking arm :04 to its unlocked position leaves the .manual" switch ll free for actuation. Should it be desired to discontinue the synchronous-control by moving the manual-autom'atiflswiteh 58 to its "manuar position, it should now be apparent that the ing the respective manuar' switches I9 and ii on" and o until the rmpectlve governors It and I! are adjusted to the desired position. To prevent over-control of either of the governors l4 and i and thereby prevent over-speeding or With the synchronizing system connected and the engine so that if the threaded member is is moved too i'ar forward the gear 23 will engage and close the limit switch 2 or if the threaded member ll is moved too far backward, the gear 12 will engage and close the limit switch m.- The limit switches 2H and II! are both connected to close a circuit which energizes a relay III to open the normally closed interlock contacts I02 and H5. The circuit for the limit switch 2H may be traced from the right-hand brush of the generator 54 through the ground connections 62, the limitswitch 2| l, a conductor 1", the normally-closed switchcontacts Ill and through the energizing winding of the relay 2", and the conductor 1 ll under-speeding of the engines fl and ii, I have provided means establishing predetermined limits of operation of the electric motor devices either manually controlled meters or as differential when these devices are operated as independent so motors during synchronous control. In addition, I have provided indicating means by which the operator may be informed should over-control or excessive operation of either or both of the elec-- tric motor devices 26 and {I occur accidentally or by improper operation. In short, a separate control limiting means and indicating means is 'ator ll. l

ht 2|! indicates that the to the left-hand brush of the generator M. Similarly the limit switch III-is in a circuit which extends from the right-hand brush of the generator I to th ground connections 62, the limit switch III, a conductor 2", the normallyclosed contacts 2" and through the energizing winding of the relay 2|! and the conductor Ill to the left-hand brush of 'the generator 54.

' During normal operation of the electric motor device II as a diflerential motor in synchronizing control, it will be remembered that the stator 80 is energized by the generator II through the normally-closed interlock contacts I02 and H6 of the relay Ill. Should for some reason the operation of the differential motor 28 move the gear ll beyond its normal operating limits and into engagement with either of the limit switches Ill-and 2l2, it is apparent that the energizing winding .of the relay III will be energized through the short circuit established from the from the stator n of the differential motor 2s and cause the motor to cease operation. Simultaneously also, opening of the interlock contacts I! and Ill will serve to deenergize the windings of the clutch operating solenoid 3! for disengaging the clutch 33. Obviously then, further adjustment of the governor It will cease, its position being held by the braking actionof the disengaged clutch member 83 against the fixed member 3'. Siinultaneouslywith the deenergization of the stator II and the disengagement of the clutch ,the normally-closed contacts ill will be engaged to energize and light a signal lamp III which indicates to the operator the fact that the electric motor device 26 has exceeded its control limits. The circuit for the indicating lamp ill traced from the middle brush of the generator 84 includes the conductor Mi, a con- 'ductor 2", the contacts I, a conductor III, a

limiting resistance 22!, the indicating lamp lit, the conductor Ill and through th ground connections 82 to the right-hand brus of the gener- Sine the S nal electric motor device It has exceeded its control limits, steps may be. taken. to correct this condition by turning the manual-automatic" switch it to its manual position for disconnecting the synchronizing system. The electric motor device 2 may then be operated as an independent manually controlled reversing motor both by disengaging its clutch and by Wholly Ol through the manual switch 59 as previously operated to adjust the governor ll described. as isf'the electric motor we. maybeoperatedinsuchamannerasisnecessary to bring the governor M back within its. predetermined control limits. To assure thatthe electric motor device '20 is operated in the cor, rect direction to return the governor setting .within the'predeterminedlimits, means are provided to prevent operation or the electric motor device II in what-might be termed the wrong mu m am he deenergized-to close a ain the interlock contacts I02 and I i i which were opened by this relay. 't'lhe normally closed contacts Ill suitably are arranged for operation to the open posi only when. the "manual" switch 59 is moved to its "up" position. Similarly; the normally-closed-contacts Ill suitably are arranged for operation to the open position only when the "manuaP switch I is operated to its down" position. In this way, it the manual" switch I! is operated to the down" position when the limit I switch III is closed, the energizing winding of Ill ior'the electric motor device I should be readily apparent. These limit switches corre- "switch 0. To get operathe relay III will continue to be energized through the normally-closed contacts 214, and

independent manuai'control of the electric motor device 26 'in the wrong direction is prevented since the main interlock contacts I02 and I i remain open; However, if the manual switch 59 is moved to the .up'position, that is, correctly actuated to operate the electric motor device 28 in a direction to 'returnthe governor within its predetermined, control limits, then the normallyclosed contacts 2 will be opened for deenergizing the relay Iii, thereby permitting the main interlock contacts 182 and H5 to close and complete the independent manual control circuits i'rom the generator 54 to the electric motor device". Thus, it is seen that operation of the electric motor device 26 in the correct direction is arbitrarily assured. As soon as the gear 22 is moved back to its proper position, the limit switch may be arranged to resume its normal open position by spring means orthe like.

In a somewhat similar manner, it the electric motor device is operated as an independent manuaily controlled motor and is accidentally over governor ll beyond its predetermined control limits, one switches ill or ill again closes the energizing circuit tor the relay Ill. Immediately the main interlock contacts In and III are opened andthe motor as well as theclutch-operating solenoid II- are deenergizcd. Thus, further operationoithemotorltinthedirectionithad then beenproceeding is denied and only opposite operation of this motorsuiiicient to return the within its predetermined control limits may be had. This latter is true because of the necessity of breaking the energizing circuit or the relay!" through the proper. one or the normally-closed contacts Ill and Ill depending oithelimit,

upon which of the limit switches Iii or II was closed.

Prom the description above, it is now thought that the operation or the limit switches "I and spond exactly in function and operation to the limitswitches Ill and III of the electric motor device 20. In short, closure of either of the limit switches III or! energizes a signal lamp 288 which indicates to'the operator that the governor It has been over-controlled. Simultaneously a 52 of the electric motor device ll. The setting of the governor II is then maintained by the braking elect oi" the deenergized or disconnected clutch ll. when it is desired to return the governor setting back within its predetermined control limits, this may be done by operating the electric motor device 4| as an independent manually controlled motor through the manipulation of the manual switch I whichagain is only eilective to operate the electric motor device in the correct direction. This is true since the proper one of the normally-closed contacts 235 and 2 which are connected ior actuation with the "manual switch must be opened to deenergize the relay III for again permitting the main interlock contacts and ill to close. Thus, as beiore, correct operation of the electric motor device in the right direction is arbitrarily assured.

While I have shown a particular embodiment of my invention, it will be understood, of course, that I do not wish to be limited thereto since many modifications may be made, and I therefore contemplate by theappended claims to coverany such modifications as fall within the true spirit and scope oi; my invention.

What I claim as new and desire to secure .by Letters Patent oi the United States, is:

1; A speed and synchronizing control system for a power-plant comprising speed controlling means for said power plant, an impulse generator driven by said power plant, means including a reference impulse generator for establishing a reference speed, an electric motor device operatlvely connected to operate said speed controlling means, said electric motor device being provided with a stator winding and with a rotor winding, switching means for connecting said stator and rotor windings respectively to said generators so that the rotor of said motor device turns in accordance with the diilerence between the speeds or said generators'and operates said speed controlling means to maintain the speed of said power plant in a predetermined relation with the speed or said reierence generator, electric sup y connections, and a second switching means (or connecting one of said windings to said supply connections and providing a closed circuit tor the other of said windings to eiiect operation oi said motor device an induction motor to operate said speed c trolling means and change the speed of said power plant.

2. A speed and synchronizing control system;

tric motor device being provided with a poly-circult stator winding and with a poly-circuit rotor winding, switching meanspfor connecting said statorand rotorwindings respectively to saidgenerators whereby the rotor of said motor device turns in accordance with the difference between the speeds of said generators and operates said speed controlling means to maintain the speed of said power plant in a predetermined relation with the speed of said reference generator, elecwe supp y connections, and manually operated switching means for short circuiting one of said windings of said motor device and for connecting the other winding of said motor device to said supply connections for operation of said motor device as a manually, controlled motor to operate said speed controlling means and change the speed of said power plant.

3. A speed and synchronizing control system for a power plant comprising speed controlling means for said power plant, a polyphase alternating current generator driven by said power plant, means including a reference polyphase generator for establishing a reference speed, an electric-motor device operatively connected to operate said speed controlling means said electric motor device being provided with a polycircuit stator winding and with a poly-circuit rotor winding, switching means for connecting said stator and rotor windings respectively to said generators whereby the rotor of said motor device turns in accordance with the difference between the speeds of said generators and operates said speed controlling means to maintain the speed of said power plant in a predetermined relation with the speed of said reference generator, and a second switching means for connecting one of said windings tonne of said generators for operation of said motor device as an induction motor to operate said speed-controlling means and change the speed of said power plant.

4. A speed and synchronizing control'system for a power plant comprising an adjustablespeed controlling means for said power plant, an electric generator driven by said power plant, means including a reference generator for establishing a reference speed, an electric motor-device arranged to be operatively connected for adjusting said speed controlling means of said power plant,

said electric motor device having separately energizable stator and rotor windings, means for subjecting said electric motor device to the ef-. fects of phase differences between the outputs of said iirst-mentioned'generator and said reference speed generator and for operating said elecaseases generator for operation of said electric motor device as anelectric differential motor thereby to control the speed of said power plant with respect to said reference speed, switching means for manually controlling the energization of said windings for operation of said electric motor device as a motor to effect speed control of said power plant independently of the relative speeds of said generators, and means establishing predetermined limits of operation for said electric motor device either when said electric motor device is operating as a differential motor or as an" independent manually controlled electric motor whereby predetermined overspeed and underspeed adjustment of said power plant is avoided.

6. A speed and synchronizing control system for a power plant comprising an adjustable speed controlling means for said power plant, an electric generator driven by said power plant, means including a reference generator for establishing a reference speed, an electric motor device arranged to be. operativelyconnected for adjusting said speed controlling means of said power plant,

said electric motor device having separately energizable stator and rotor windings, means for subjecting said electric motor device to the'efl'ect of phase differences between the outputs of said first-mentioned generator and said reference speed generator and for operating said electric motor device as a differential motor thereby to control the speed of said power plant with respect to said reference speed, switching means for short-circuiting a predetermined one of said windings and for energizing the other of said windings from a predetermined one of said generators to effect independent manual control of said electric motor device and thereby speed control of said power plant independently of the relative speeds of said generators, and means establishing predetermined limits of operation forsaid electric motor device by interrupting the energization of said electric motor device for preventing predetermined overspeed and underspeed adjustment of said power plant.

7. In a multiple power plant speed and synchronizing control system in which each power tric motor device as a differential motor thereby to control the speed of said power plant with respect to said reference speed, and switching v means for energizing said stator windings of said electric motor device from said first-mentioned generator and short-circuiting said rotor windings for converting said electric motor device toan induction motor toenable independent manual control of said power plant.

5. A speed and synchronizing control system for a power plant comprising an adjustable speed controlling means for said power plant, an electric generator drivenby said power plant, means including a reference generator for establishing a reference speed. an electric motor device arrangedto be operatively connected for adjusting said speed controlling means of said power plant, said electric motor device having separately energizable stator and rotor windings, means for subjecting said windings to the effects of phase differences between the outputs of said firstmentioned generator and said reference speed plant is provided with a speed controlling means, the combination of an electric motor device for operating each of said speed controlling means,

each of said motor devices being provided'witha stator winding and a rotor winding, an impulse current generator driven by each of said power plants, switching means for connecting one of said windings of each of said motor devices to one of said generators and for short-circuiti-ng the other of said windings to provide for operation as an electric induction motor to operate its speed controlling means, and a second switching means for connecting the windings of one of said motor devices respectively to the generator driven by its power plant and to a pr determined other one of said generators for operation as an electric differential device to maintain the speed of its powerplant in a predetermined relation with the speed of the power plant driving said p'edetermined generator. A

it. In a multiple power,plant speed and'synchronizing control system in which each power plant is provided with an adjustable speed governing means, the combination ofan electric motor device for adjusting each of said governing means, said motor devices beinge'ach'provided with a poly-circuit 'stator winding and with a poly-circuit rotor winding, a polyphase generator driven by each power plant, switching means for connecting the windings one of said motor devices respectively to the generator driven by its power plant and to a predetermined other one of said generators for operation of said motor device as an electric differential to, control the speed of its power plant in a predetermined relation with the speed, of the power plant driving said predetermined generator, a second switching means for energizing one of said windings 01' each of said electric motor devices foroperation of each of said motor devices as an electric motor to effect control of the speed of the power plant controlled by said-motor device independently of any other of said power plants, and limit switch control means for each of said electric motor devices operated by a predetermined oper- ,ation of each motor device in each directionthereby to preclude predetermined overspeed and underspeed adjustment of the respective power lants.

9. In a multiple power plant speed and synchronizing control system in which each power plant is equipped with an adjustable speed controlling means, the combination including an electric motor for adjusting each ofsaid speed controlling means, a "generator driven by each power plant, means including a switch for interconnecting said generators and said electric motors to establish one of said power plants as a master power plant and automatically to synchronize the speeds of the remaining power plants with the speed of said master power plant for efiecting automatic control of said power plants, switching means for individually controlling the operation of each of said electric motors as an independent manually controlled electric motor for eflecting manual control of its respective one of said speed controlling means independently or said synchronizing means, limit means establishing predetermined control limits for said electric motors to prevent excessive plant is equipped with an adjustable speed controlling means, the combination including an electric motor device for adjusting each of said speed controlling means, an electric generator driven by each power plant, switching means including a plurality of manual switchesfor individually controlling the operation of each of said electric motor devices as a manually controlled electric motor for effecting independent manual control of said power plants, means including a manual-automatic" switch for interconnecting said generators and said electric motor devices to establish one of said power plants as a'master power plant and automatically to synchronize the speeds of the remaining power plants with the speed of said master power plant for effecting automatic control of said power plants, means including a selector switch for selecting a predetermined one of said power plants as the master power plant subject to independent manual control by its respective electric motor device through said individual switching means, and interlocking means operatively connecting said switches for locking predetermined ones of said manual switches in an oil position during automatic synchronizing control and for, simultaneously maintaining the manual" switch free for operation.

11. A speed and synchronizing control system for a power plant comprising an adjustable speed controlling means for said power plant, an electric generator driven by said power plant, means including a reference generator for establishing a reference speed, an electric motor device arranged to be operatively connected for adjusting said speed controlling means of said power plant, switching means for subjecting said electric motor device to the effects of phase differences between the outputs of said first-mentioned generator and said reference speed generator and for operating said electric motor device as a differential motor thereby to control the speed of said power plant with respect to said reference speed, "manual" switching means for converting said electric motor device to an induction motor to enable independent manual control of said power plant without regard to the relative speeds of said generators, and interlocking means operatively connecting said switching means to prevent manipulation of said manual switching means during diiferential operation of said electric motor device.

12. In a multiple power plant speed and synchronizing control system in which each power plant is equipped with an adjustable speed controlling means, the combination including an electric motor device for adjusting each of said speed controlling means, a generator driven by each power plant, means including a plurality of manual switches for individually controlling the operation of each of said electric motor devices as an independent manually controlled electric motor for efiecting manual control of said power plants, means including a manual-automatic switch for interconnecting said generators and said electric motor devices to establish one of said power plants as a master power plant and automatically to synchronize the speeds of the remaining power plants with the speed of said master power plant for effecting automatic control of said power plant, limit means establishing predetermined control limits for said electric motor devices to prevent excessive control operation thereof and thereby preclude predetermined overspeed and underspeed ad- Justment'of the respective power plants, and

interlocking means operatively connecting said electric motor device for adjusting each of said speed controlling means, a generator driven by each power plant, switching means for .individually controlling the operation of each of said said power plants as a master power plant and automatically to synchronize the speeds of the remaining power plants with the speed of said master power plant for efiectingautomati'c control of said power plant, limit means establishing predetermined control limits for said electric motor devices to prevent excessive control operation thereof and thereby preclude predetermined overspeed and underspeed adjustment of the respective power plants; said individual switchin: means enabling return operation of said electric motor devices back within said predeteraaeases mined control limits after operation of said limit means, means disabling said individual switching means'from effecting operation of ,said electric motor devices other than in a proper return direction after said predetermined control limits have been exceeded, and" interlocking means operatively connecting said individual switching means and said switch for predetermining the operability of said individual switching means 10 relative to the position oi. said switch.

L AURENS' A. TAYLOR. I 

